Mask deformation and flow leakage during pulsatile expiratory events

It is well established that diseases can be spread by airborne transmission, as small infectious particles are generated during respiratory events such as talking and coughing. One strategy to reduce disease transmission via expiration is the use of face maks. However, gaps between the mask and face result in flow leakage. In this work, the flow leakage around a surgical mask is studied. Using a pulsatile coughing simulator, mask deformations are measured using stereophotogrammetry for single- and double-pulsed (SP,DP) coughs at different cough peak flow rates (CPFR). Using finite element method modelling, these deformations are reproduced using a Kirchoff-Love plate model. Experiments reveal that the mask does not return to its initial position between pulses during a DP cough. This is consistent with previous findings that a DP cough generates greater leakage than a SP event. Furthermore, it is found that the maximum mask displacement does not linearly increase with CPFR. It is suggested that this correlates with observations that the normalized flow leakage out the side of a surgical mask is larger for smaller CPFR single-pulsed coughs.